Study On The Regulation Of Mating Behavior By Tachykinin In Daphnia Sinensis

Tachykinin(TK)and its analogue Natalisin(NTL)are ubiquitous in central and peripheral tissues.Their receptors can interact with a variety of second messenger systems and participate in physiological functions such as reproductive regulation,gastrointestinal smooth muscle relaxation and contraction,and body pain transmission.In mammals,members of the tachykinin family enhance male aggression.In invertebrates,NTL knockdown reduced the mating desire of insects significantly.The above results indicate that tachykinin and its analogues play an important role in regulating animal mating,but their function in regulating sexual mating behavior in cladocerans are unclear.In this study,Daphnia sinensis(Wuhan,Nanhu)was used as the research object.Firstly,sequence analysis and ligand-receptor selectivity analysis of TKs,NTLs and their receptor TKRs were carried out by referring to the existing Daphnia sinensis genome in our laboratory.Then,the effects of different genders and environmental factors(population density and light)on the expression of TK and its receptors were verified.Finally,TK was used to treat Daphnia sinensis` to verify its effect on male mating behavior,and the related pathways of TK-induced male mating behavior were analyzed by transcriptome combined with metabolomics.The mature peptides of TKs and NTLs of Daphnia sinensis have their own conserved amino acid termini,and the seven α-helix structures predicted in three-dimensional model of their receptor TKRs.The results of ligand-receptor selectivity showed that TKR1 was the specific receptor of TK1,TKR2 was the specific receptor of NTLs,and TKR3 was the specific receptor of TK2,TK3 and NTL4.The expression of TKs and NTLs were higher in males,and the expression of TKR1 increased with the increase of population density or the decrease of light duration.This result indicates that high population density or dark environment may induce male mating behavior through the mediation of TK and its receptor TKR1.The results of soaking experiments showed that TK1 induce the mating behavior of female and male Daphnia sinensis significantly.In addition,TK1 treatment induced the heart rate and oxygen consumption rate of Daphnia sinensis and make their body color red significantly.Interestingly,the body color of male was also reddish,and the heart rate and oxygen consumption rate were significantly higher than those of female in Daphnia sinensis.The above results suggested that TK1 enhance the mating behavior of Daphnia sinensis by enhancing their oxygen consumption capacity.In order to further reveal the mechanism of TK1-induced mating behavior in Daphnia sinensis,we used transcriptome combined with metabolome to compare the transcriptional and metabolic differences between male and female,and the changes of transcriptional and metabolic levels in Daphnia sinensis after TK1 treatment.The results showed that:(1)TK1 significantly induced heme transporter activity,which indicates that TK1 can enhance the demand for oxygen by improving the ability of hemoglobin to carry oxygen.(2)TK1 treatment significantly decreased the level of glycerophospholipids in Daphnia sinensis,and the level of glycerophospholipids in male Daphnia sinensis was also significantly lower than that in Daphnia sinensis.These results indicated that TK1 may be involved in the regulation of male mating behavior by inducing glycerophospholipid metabolism.(3)TK1 treatment significantly increased the level of 6-β-hydroxytestosterone in Daphnia sinensis,and the level of this male hormone in male Daphnia sinensis was also significantly higher than that in Daphnia sinensis,suggesting that TK1 may regulate the mating behavior of Daphnia sinensis by inducing the secretion of 6-β-hydroxytestosterone.